The present invention relates to an epidural space locating device for detecting the epidural space while protecting the dura mater in the spinal column of humans. In particular, the present invention relates to a spinal epidural space locating device that maintains positive pressure within a bellows chamber until the epidural space is located, and at which time zero or negative pressure more easily permits the collapsing of the bellows chamber of the epidural space locating device. In accordance with the present invention, this change of pressure is preferably sensed by a visual collapsing of the bellows chamber and/or reduction of pressure against a thumb of the hand operating the epidural space locating device. Methods of using such an epidural space locating devices are also provided.
As is well known, to avoid the side-effects of drugs on the brain, analgesic or anesthetic drugs can be delivered to the spinal cord by placing the drugs outside of the membranous sac containing the spinal cord. Between this sac, called the dura, and the overlying spinal ligaments, is a space called the spinal epidural space. Placing drugs in the spinal epidural space blocks spinal cord functions including pain transmission.
In practice, locating the spinal epidural space with a needle requires great care because it is difficult to sense the change in resistance as the needle passes through the spinal ligaments. It is desirable to reach the epidural space and stop before going through the dura. The concern, and therefore risk in the procedure, is the undesirable puncture of the dura. Identification of the precise moment when the needle is advanced into the epidural space is thus very desirable.
Present methods for identifying this space fall into two main categories: the xe2x80x9closs of resistancexe2x80x9d and the xe2x80x9changing dropxe2x80x9d techniques. The xe2x80x9closs of resistancexe2x80x9d method is the most commonly used technique to identify the spinal epidural space. The xe2x80x9closs of resistancexe2x80x9d technique involves direction of the epidural needle through the skin into the interspinous ligament. One example of a device that utilizes the xe2x80x9closs of resistancexe2x80x9d technique is described in U.S. Pat. No. 5,902,273 to Yang et al. Yang et al describe a combination of a pressure chamber, syringe to build up pressure within the pressure chamber, and indicator section with a corresponding pressure indicator bar to indicate a loss of pressure within the pressure chamber. Specifically, Yang et al describe a device and method whereby a one-way valve for positive pressure build-up and an attached pressure indicator identifies the loss of positive pressure when the needle enters the epidural space. In particular, when the plunger is pulled outwardly, air will be drawn to the syringe housing, and when the plunger is thereafter pushed inwardly, air will be pushed into the pressure chamber through the one-way valve. When the epidural needle reaches the epidural space, the positively pressurized air will deflect the dura mater away from the needle tip as it escapes from the chamber, through the needle, and into the epidural space. The positive pressure in the chamber will drop immediately, and an indicator will return to its original position due to a corresponding spring force.
Other less intricately constructed devices are also well known. For example, another commonly used device is the free sliding glass syringes, or with improved plastic materials, a more or less free sliding plastic syringe. In these examples, when the needle tip is properly positioned within the substance of the interspinous ligament, depression of the syringe plunger by a thumb will not be possible. As the needle is advanced, the injecting hand is placed on the plunger of the syringe with continuous pressure. As the needle passes through the ligamentum flavum and enters the epidural space, a sudden loss of resistance within the syringe occurs and this change of pressure can be sensed by the ease by which the plunger is slideable within the syringe. The medication can then be injected into the epidural space in a known manner.
It is perceived that the construction of the epidural space locating device described by Yang et al is unduly complicated. Moreover, there are several disadvantages in using aforementioned free-sliding glass or plastic syringes. In particular, extreme experience is needed to maintain the required alignment between the plunger and the longitudinal bore of the syringe. Inadvertent and thus undesirable angling of the plunger against the inner side walls of the syringe results in friction therebetween and possibly hindering the ability to recognize, precisely locate and time the locating of the epidural space. While this problem is not as common with glass syringes, the problem is more pronounced and common with syringes made of plastic. While it would therefore appear that continued use of free-sliding glass syringes may be acceptable, it is well known that such syringes are undesirably expensive.
Therefore, it is desirable to provide an epidural space locating device that overcomes the foregoing perceived disadvantages and achieves the objectives set forth below.
It is therefore an object of the present invention to provide an improved epidural space locating device that overcomes the foregoing perceived deficiencies.
It is another object of the present invention to provide an improved epidural space locating device that more easily allows a user to locate the epidural space for epidural anesthesia or analgesia, among other things.
It is yet another object of the present invention to provide an epidural space locating device that has enough positive pressure to effectively deflect the dura mater upon entrance of the needle into the epidural space, thus effectively preventing dural puncture.
It is still a further object of the present invention to provide an epidural space locating device that can be made smaller and less cumbersome than prior art devices.
It is still another object of the present invention to provide a user with an improved epidural space locating device that provides for reliable needle advancing and epidural space locating.
Another object of the present invention is to provide the epidural space locating device operator with an immediate indication of xe2x80x9closs of positive pressurexe2x80x9d for ease of use and training, and one that is more consistent with devices already known in the art.
An additional object is to provide an improved epidural space locating device that achieves all the advantages provided by a free-sliding glass syringe but which is significantly less costly to manufacture.
Still another objective of the present invention is to provide an improved epidural space locating device that does not require the precise alignment required by present known plungers and syringes.
And yet another objective of the present invention is to provide a locating device that utilizes a collapsible bellows within which a loss of resistance can be sensed or otherwise felt by the operator, such as by the operator""s thumb thereby providing the operator with the desired xe2x80x9cfeelxe2x80x9d that the operator was previously used to.
Yet another object of the present invention is to provide an epidural space locating device that can be filled with saline solution in another embodiment utilizing the xe2x80x9closs of resistancexe2x80x9d technique.
Still another objective of the present invention is to provide methods of using an epidural space locating device constructed in accordance with the present invention.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The invention accordingly comprises the features of construction, combination of elements and arrangement of parts and sequence of steps which will be exemplified in the construction, illustration and description hereinafter set forth, and the scope of the invention will be indicated in the claims.
Generally speaking, in accordance with the present invention, an epidural space locating device for locating an epidural space, is provided. In one embodiment of the invention, the device may comprise a body section having a first end and a second end and a longitudinal passageway extending therethrough, the first end of which is coupleable to a luer assembly; and a collapsible bellows chamber having one end coupled to the second end of the body section and the other end exposed so as to permit pressure to be exerted thereon by one or more digits of a hand, wherein positive pressure within the bellows chamber maintains the integrity of the shape of the bellows chamber and wherein negative or zero pressure within the bellows chamber facilitates the collapsing of the shape of the bellows chamber thus indicating the locating of the epidural space by a needle that is coupled to the luer assembly as the needle enters the epidural space; wherein the loss of pressure within the bellows chamber is sensed by the one or more digits of the hand as the shape of the bellows chamber collapses.
The present invention may also incorporate a luer lock, coupled to the first end of the body section, for air-tightly coupling a needle to the body section and a needle assembly, comprising a needle hub and epidural needle, coupled to the luer lock. Preferably, the bellows chamber includes a neck portion, the neck portion being air-tightly coupled to the second end of the body section, and wherein the neck portion has an air passageway that is inline with the longitudinal passageway extending through the body section. In a particular embodiment, the bellows chamber and the neck portion may be integrally formed and the neck portion and the first end of the body section are threadably coupled. The first end of the bellows chamber may include a concave surface for supporting the thumb of the hand, wherein the negative or zero pressure within the bellows chamber is detected by the thumb of the hand as the bellow chamber collapses. In yet a particular configuration, the bellows chamber may be made of polyethylene or rubber, or other sufficiently flexible material.
In yet another embodiment of the present invention, a method for detecting the entry of a needle into the epidural space of a patient is provided. In this embodiment, the method may comprise the steps of providing an epidural space locating device comprising a body section having a first end and a second end and a longitudinal passageway extending therethrough, the first end of which is coupleable to a luer assembly; and a collapsible bellows chamber having a first end coupled to the second end of the body section and a second end exposed so as to permit pressure to be exerted thereon by one or more digits of a hand, wherein positive pressure within the bellows chamber maintains the integrity of the shape of the bellows chamber and wherein negative or zero pressure within the bellows chamber facilitates the collapsing of the shape of the bellows chamber thus indicating the locating of the epidural space by a needle that is coupled to the luer assembly; coupling a luer assembly and epidural needle to said locating device; inserting the needle into a patient towards the patient""s epidural space; and continuing to insert the needle towards the patient""s epidural space while applying pressure against the second end of the bellows chamber by a digit of a hand until the shape of the bellows chamber begins to collapse, thereby indicating entrance into the epidural space.
In this embodiment, the method may include the step of sensing a drop of pressure in the bellows chamber by the thumb of the hand which is against the second end of the bellows chamber. As would be understood, the method may include the step of inserting the needle into at least the interspinous ligament as the needle is moving towards the epidural space. In one preferred methodology, the invention would include the steps of introducing a solution, such as but not limited to saline, into the bellows chamber; inserting the needle into a patient towards the patient""s epidural space; and continuing to insert the needle towards the patient""s epidural space while applying pressure against the second end of the bellows chamber by a digit of a hand until the shape of the bellows chamber begins to collapse by the solution being introduced into the epidural space, thereby indicating entrance into the epidural space. Here, the solution may be introduced into the bellows chamber as the second end of the bellows chamber is pulled in a direction away from the body section.
Lastly, the present invention is directed to a method for deflecting a patient""s dura for preventing dural puncture, in which the method comprises the steps of providing an epidural space locating device comprising a body section having a first end and a second end and a longitudinal passageway extending therethrough, the first end of which is coupleable to a luer assembly; and a collapsible bellows chamber having a first end coupled to the second end of the body section and a second end exposed so as to permit pressure to be exerted thereon by one or more digits of a hand, wherein positive pressure within the bellows chamber maintains the integrity of the shape of the bellows chamber and wherein negative or zero pressure within the bellows chamber facilitates the collapsing of the shape of the bellows chamber thus indicating the locating of the epidural space by a needle that is coupled to the luer assembly; coupling a luer assembly and epidural needle to said locating device; inserting the needle into a patient towards the patient""s epidural space; and continuing to insert the needle towards the patient""s epidural space while applying pressure against the second end of the bellows chamber by a digit of a hand until the shape of the bellows chamber begins to collapse, thereby deflecting a patient""s dura for preventing dural puncture.
Similarly, the method may include the step of sensing a drop of pressure in the bellows chamber by a thumb of the hand against the second end of the bellows chamber and/or inserting the needle into at least the interspinous ligament as the needle is moving towards the epidural space. Likewise, the method in accordance with the present invention may include the steps of introducing a solution into the bellows chamber; inserting the needle into a patient towards the patient""s epidural space; and continuing to insert the needle towards the patient""s epidural space while applying pressure against the second end of the bellows chamber by a digit of a hand until the shape of the bellows chamber begins to collapse by the solution being introduced into the epidural space, thereby indicating entrance into the epidural space.